The present invention relates to a method of applying grease to smooth the mechanical operations of members at their contact region. More particularly, the invention relates to a method of applying grease in measured amounts, the components of the grease being separable.
Various methods of providing a lubricant such as grease to the contact region of mechanical members, such as in a sliding region or bearing region of mechanical members, have been employed in a variety of industrial fields. Grease is, in general, highly viscosity, and it is rather difficult to apply precisely measured quantities of grease to desired parts.
One conventional method for applying measured quantities of grease is carried out with the apparatus shown in FIG. 1.
The apparatus shown in FIG. 1 uses a closed system to automatically supply precisely measured quantities of grease at predetermined time intervals. The apparatus is used, for instance, to apply grease to the shaft of a roller for guiding the magnetic tape in a magnetic tape cassette.
The apparatus of FIG. 1 employs a closed system in which a grease applying head 30 operated by an air cylinder 40 is connected through a grease supplying pipe 38 to a grease tank 39 storing grease 20. The grease applying head 30 includes a large diameter part 31, a plunger 32 movable in the large diameter part 31, a pushing pin 33 positioned at the end of the plunger 32, and a grease applying nozzle 37 extending from the outer cylindrical wall of the large diameter part 37. When the air cylinder 40 is operated, the grease applying head is suitably operated with the aid of stoppers 41 and 42 so that a precisely measured quantity of grease is automatically dispensed.
The operation of the apparatus shown in FIG. 1 will be described in more detail. The grease applying head 30 is moved, in its entirely, by the air cylinder 40. In this operation, the large diameter part 31 is stopped by the first stopper 41 when the grease applying head 30 has moved a predetermined distance, while the plunger 32 continues to move. As the plunger 32 moves forwardly in this manner, the pushing pin 33 at the end of the plunger 32 enters a grease pool 34, being pushed by the second stopper 42. In this operation, a communication port 35, through which the grease supplying pipe 38 and the grease pool 34 are communicated with each other, remains closed because the plunger 32 is shifted from the large diameter part 31, whereas the grease pool 34 is communicated with the grease applying nozzle 37 through another communication port 36.
Therefore, as the pushing pin 33 enters the grease pool, a suitable quantity of grease 20 is discharged through the grease applying nozzle 37 and applied to a supporting shaft 14. Thereafter, the grease applying head 30 is moved backwardly (in the direction of an arrow Y) by the air cylinder 40, thus receiving grease from the grease tank 39.
The above-described operations are repeatedly carried out. The operation of the grease applying head 30 is started in response to a signal which is produced when, for instance, a conveying device such as a pallet reaches a predetermined position. The grease 20 is delivered from the grease tank 39 under an air pressure of the order of 4 kg/cm.sup.2.
Heretofore, in the case where it was required to repeatedly supply a predetermined amount of high-viscosity grease to a predetermined position with high accuracy, an apparatus for applying or injecting the grease with the above-described closed system of relatively complex construction has been extensively employed. However, the apparatus suffers from the following difficulties:
When the grease 20 is initially charged into the grease tank 39 or the grease tank 39 refilled, air unavoidably enters the closed system, which should be completely filled with the grease 20. In order to eliminate this difficulty, a valve 43 is connected to the grease supplying system to remove the air-mixed grease from the closed system. However, it is considerably difficulty to completely remove the air-mixed grease. Therefore, when the air remaining in the system is supplied into the plunger 32, the quantity of grease 20 discharged from the grease applying nozzle 37 fluctuates.
The grease 20 may contains, for instance, "LUBRIPLAT Aero" (trade name). In this and some other types of grease, the components are separable; i.e., the solid components are separable from the oil components. In such a case, the components can separate in the closed system, and hence the grease is applied in a separated state. Such grease cannot function properly. Also, sometimes the oil components can leak from the closed system and adhere to the lower half 13 of the cassette.
Since the grease 20 is always viscous to some extent, some tends to collect on the end of the grease applying nozzle 37. Especially in the case where the above-described grease applying method is employed, grease can gradually accumulate, on the end of the nozzle. A blob of the grease thus accumulated may be transferred at once to the area to be lubricated. That is, the quantity of grease applied is not stable.